This tells several interweaving stories:
1. How a young lawyer, Derville, got a start in life.
2. The history of the usurer, Gobseck.
3. What happened to the Restaud family after the Comtesse de Restaud pawned the family diamonds to pay her lover’s debts (first mentioned in ‘Old Goriot’).

I’ve checked the PG textfile against the Pléiade French edition and restored accents. Curiously, the last couple of paragraphs were missing from the translation, so I translated those too.
(Actually, I think that the story reads better without them but, if Balzac wrote them, then in they go.)